Vehicle pitch control device

ABSTRACT

A preferred embodiment of a pitch control device for a vehicle leveling system includes a pair of leveler unit associated with primary suspension springs in the rear suspension of a vehicle. The pitch control includes sensing bellows at the front and at the rear of the vehicle which are operative to produce a pressure differential when the vehicle frame and chassis are pitched either from front to rear or from rear to front of the car and wherein a valve controller responds to the pressure differential to regulate the levelers to compensate for the pitched relationship. Other embodiments are illustrated.

United States Patent [191 Klees Feb. 13, 1973 VEHICLE PITCH CONTROLDEVICE [75] Inventor: Gerard T. Klees, Rochester, Mich.

[ 7 3 Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: July 19, 1971 [2]] Appl. No.: 163,833

[52] [1.5. CI. ..280/l24 F, 280/124 LR, 267/65 D I [51] Int. Cl ..B60g17/04 [58] Field of Search ..280/l24 F, 124 LR, 6

[56] References Cited UNITED STATES PATENTS 2,954,237 9/1960 Sampietro..280/l24 F Primary ExaminerPhilip Goodman Assistant Examiner.lohnCarroll Attorney-W. S. Pettigrew et al.

[5 7 ABSTRACT A preferred embodiment of a pitch control device for avehicle leveling system includes a pair of leveler unit associated withprimary suspension springs in the rear suspension of a vehicle. Thepitch control includes sensing bellows at the front and at the rear ofthe vehicle which are operative to produce a pressure differential whenthe vehicle frame and chassis are pitched either from front to rear orfrom rear to front of the car and wherein a valve controller responds tothe pressure differential to regulate the levelers to compensate for thepitched relationship. Other embodiments are illustrated.

6 Claims, 6 Drawing Figures VEHICLE PITCII CONTROL DEVICE This inventionrelates to automatic vehicle leveling systems and more particularly toan automatic vehicle leveling system that compensates for changes inload and that also compensates for changes in the pitch attitude of thevehicle.

Automatic leveling systems utilizing either a vacuum leveler unit or apressurized hydraulic or air pressure leveler unit often include a pairof levelers located between the rear axle housing of a vehicle and theframe thereof. These systems are operative to produce a supplementalload carrying capacity in addition to that of the primary suspensionsprings of the vehicle to maintain a desired height relationship betweenthe car chassis and the axle assembly.

In such systems the car frame and chassis are maintained essentiallylevel when the car is either loaded or unloaded between a curb heightload weight and a full rated load condition. However, there are caseswhere greater loads are concentrated rearward of the axle of the car;for example, in a station wagon cargo area or in the trunk of a sedan.This can cause the front end of the vehicle to pitch upwardly eventhough the rear height of the car is maintained by the leveler units.

An object of the present invention is to provide a system fordetermining the pitch relationship of a vehicle chassis and to providemeans for regulating the operative condition of load leveler units sothat the car pitch can be compensated.

A further object of the present invention is to improve automaticvehicle leveling systems of the type including at least a pair of loadleveler units that are adapted to be. connected between the sprung andun sprung mass of the vehicle and operated to maintain a predeterminedrear standing height relationship by the provision of pitch compensatingmeans responsive to sensor means which produce a correction signalcorresponding to the height relationship between the sprung and unsprungmass at the front of the vehicle and a like relationship between thesprung and unsprung mass at the rear of the vehicle.

Yet another object of the present invention is to provide a combinedindicator and control arrangement for indicating the pitch relationshipof the vehicle from the front tothe rear thereof and including means forautomatically compensating for vehicle pitch by varying the operation ofa leveler unit in an auxiliary load leveling system which is operativeto maintain a predetermined rear vehicle height.

These and other objects of the present invention are obtained in oneworking embodiment which includes a pair of primary suspension springsbetween the axle housing of a vehicle and the rear frame portion of thevehicle chassis. A pair of leveler units in the rear suspension producean auxiliary load supporting capacity.

In a preferred form, the leveler units are vacuum operated and pulleddown against the force of the primary springs to maintain apredetermined height rela- 'tionship between the vehicle frame and therear axle housing. The leveler units are selectively connected to asource of vacuum or to atmosphere by a control valve which is operatedby a pair of opposed bellows connected to a first pitch sensor bellowslocated between the sprung and unsprung mass at the front of the vehicleand a second pitch sensor bellows located between the sprung andunsprung mass at the rear of the vehicle.

When the vehicle is at a level curb position and um loaded, the pressurein the pitch sensing bellows are equal, front and rear.

Between an unloaded and a full rated load, the leveling system iscapable of maintaining a substantially level vehicle under conditionswhere load is uniformly distributed in the vehicle. However, when aheavy load is concentrated rearwardly of the rear axle of the vehicle,for example in a station wagon cargo area or a sedan trunk, the frontcan be raised or pitched upwardly. When this occurs, the sensing bellowsproduce a pressure unbalance signal which indicates the high front pitchattitude. The opposed bellows receive the signal and operate the controlvalve to regulate the leveler unit pressure to compensate for the highpitch condition.

A vacuum leveler unit will compensate the case of a heavy load in thetrunk or rearward of the axle and a front that is too as follows. First,the pair of bellows produce a pressure unbalance on the control valve tocause an atmospheric port to the leveler units to be opened. Thisreduces the vacuum in the leveler unit and causes the rear of the car tobe raised by the primary coil springs. This causes the rear heightsensing bellows pressure to increase to that in the front sensingbellows until the front and rear signal pressures are balanced. At thispoint, the control valve is returned to a balanced, closed position.When the load is removed, the reverse action occurs, and the vacuum portto the leveler unit is opened to cause it to pull down the rear to itslevel position.

The controller preferably is located on the instrument panel of avehicle and has a scale which indicates the pitch condition. In onepreferred embodiment, the indicator is a pointer that extends from acontrol lever of the control valve.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

IN THE DRAWINGS:

FIG. 1 is a diagrammatic view of a vehicle leveling system including thecombined pitch controller and indicator of the present invention;

FIG. 2 is a top elevational view of a pitch control valve and pitchread-out device used in the system of FIG. 1;

FIG. 3 is an end elevational view of the device in FIG. 2 looking in thedirection of the arrows 3 3 in FIG. 2;

FIG. 4 is a view in vertical section taken along the line 4 4 of FIG. 2looking in the direction of the arrows with a top cover of the device inplace;

FIG. 5 is a fragmentary sectional view taken along the line 5 5 of FIG.2 looking in the direction of the arrows with the cover in place; and

FIG. 6 is a diagrammatic view of a system disclosing a second embodimentof the invention.

In FIG. 1 of the drawings, a leveling system 10 is illustrated inassociation with a frame 12 and axle housing 14 of a rear suspensionassembly 16. A pair of ground engaging wheel and tire assemblies 18 areat either end of axle housing 14. A lower control arm 20 has the rearend thereof pivotally secured by a pin 22 to an axle housing bracket 24.The front end of arm 20 is pivotally secured by a pin 26 to a framebracket 28.

The frame 12 is supported on the axle housing 14 by a pair of primarysuspension coil springs one of which is illustrated at 30. The systemfurther includes a pair of vacuum operated leveler units one of which isindicated at 32 in association with spring 30. The spring 30 and levelerunit 32 is adjacent one end of housing 14. Another spring and levelerunit, like those illustrated are at the other end of housing 14. Theunits 32 pull the frame 12 downwardly against the force of the primarysuspension springs 30 to maintain a predetermined rear heightrelationship between the frame 12 and the axle housing 14 to compensatefor load changes on the vehicle.

The system 10 is also associated with a standard front suspension of avehicle. One side of such a suspension is illustrated. It includes aground engaging tire and wheel assembly 34 having a wheel spindle 36that is connected to a steering knuckle 38 having the upper end thereofconnected to an upper control arm 40 by means of a pivot pin 42 and thelower end connected by means of a pin 44 to one end of a lower controlarm 46.

The upper control arm 40 has the opposite end thereof connected by apivot pin 48 to a front portion 49 of the car frame and the lowercontrol arm 46 is pivotally connected by means of a pin 50 to anotherportion 51 of the frame. Frame portions 49, 51 are diagrammaticallyillustrated as fixed reference points in the system and are movable withthe front end of frame 12.

A primary suspension spring 52 is located between the upper and lowercontrol arms 40, 46 to resiliently support the front part of the frame12 for movement with respect to the ground engaging wheel assembly 34and vice-a-versa. The vehicle has another front suspension sideidentical to that described. As illustrated, each one of the levelerunits 32 are located in association with a primary suspension spring 30to produce a supplemental or auxiliary load leveling effect to maintaina desired rear height relationship between axle housing 14 and frame 12.

Damping components or shock absorbers normally found in both rear andfront suspensions of vehicles are omitted in order to more clearly setforth the inventive aspects of the system 10.

Each of the rear vacuum leveler units 32 are connected to a pressurecontroller device 56 by a pressure conduit 58. In each case it has oneend in communication with the interior of a pressure bellows 60 thatdefines the side walls of the leveler unit 32 and the opposite endthereof communicating through a port 62 in a sealed controller housing64.

The controller 56 is operative to communicate the control port 62therein selectively with an atmospheric inlet pipe 66 which communicatesthrough a port 68 in the housing 64. Additionally, the controllerregulates the communication of a vacuum pipe 70 with a control port 72in the housing 64.

The controller 56 is selectively operated to maintain a predeterminedcontrol of both the atmospheric pipe 66 and vacuum pipe 70 so as tomaintain a pressure condition in the vacuum operator 32 to produce anauxiliary load support which accomplishes leveling of the vehicleincluding maintaining a predetermined level between both front and therear of the vehicle so that the frame will not be pitched either aboveor below a desired plane, preferably horizontal or near horizontal.

More particularly, as best illustrated in FIG. 2, the controller 56 hasits housing 64 arranged to bc supported with respect to an instrumentpanel 74 ofa vehicle so that an end face 76 of the controller 56 will belocated in a readily observable position. The end face 76 includes atransparent cover 78 having indicia 80 thereon which indicates a frontlow level or rear low condition thereon. A movable indicator 82 islocated with respect to the indicia 80 and is moved with respect theretoin accordance with operation of a pair of opposed differential pressurebellows 84, 86 which are located within a sealed chamber 88 of thehousing 64.

The bellows 84 is communicated through an inlet port 90 with one end ofthe control conduit 92 which has the opposite end thereof connected to arear sensing bellows 94 located with one end thereof in engagement withthe rear frame 12 which represents a sprung mass portion of the rearsuspension assembly 16. The opposite end of the bellows 94 is coupledthrough a link 96 to the control arm 20 which is part of the unsprungmass portion of the rear suspension 16.

The bellows 94 is a sealed chamber which, when the vehicle is level, hasan operating pressure of l4.7 psia.

When the system is assembled, the front and rear bellows operatingpressure is the ambient atmospheric pressure. Height changes will raiseand lower the sensing bellows pressure.

When the vehicle rear is below a predetermined height relationshipbetween the sprung mass portion or frame 12, and the unsprung massportion or axle housing 14 the bellows 94 will be compressed todischarge fluid across a control orifice section 98 in the controlconduit 92 to increase the pressure of the bellows 84.

Under this condition, the sprung mass portion at the vehicle front maymove upward with respect to the unsprung mass portion thereof.

When this occurs, a front signal bellows 100 having one end thereoflocated with respect to the frame 12 at the front of the vehicle and theopposite end thereof connected by a link 102 to the upper control arm 40or other unsprung portion of the front suspension will expand in volumeto draw fluid from a control conduit 102 having one end thereofconnected to the signal bellows 100 and the opposite end thereofconnected through an inlet port 104 in the housing 64 to bellows 86. Asfluid flows across the orifice section 106 in the control conduit 102 itwill reduce the pressure in the bellows 86.

The inner ends of the bellows 84, 86 are actively connected to a member108 which responds to the differential pressure buildup within thebellows 84, 86 to, in the case of the rear low condition, cause theindicator arm 82 to shift to the right of the scale indicated in FIG. 1.

When this occurs, the member 108 positions a first control valve 110 inan open position to communicate the sealed chamber 88 and theatmospheric pipe 66. A second valve assembly 112 is closed to sealbetween the sealed chamber 88 and the vacuum pipe 70.

The pressure increases in the bellows 60 of the leveler units 32 toincrease the upward supportive force between the frame 12 and the rearhousing portion 14 and this upward force acting in conjunction with therear springs 30 will cause the rear end to raise.

For simplicity of explanation, it is assumed that the signal bellows arelocated at a position where their deflection change equals thedeflection change of the sprung mass relative to the unsprung mass. Forproper system operation where this condition is not realized,

the following control system relationship should be met:

Where:

A control bellows eff. area R ratio of bellows travel to wheel travelA,= signal bellows eff. area V,,= initial volume of control system,including control and signal bellows dw= deflection at full rated loadIn addition to load leveling, the system will compensate for vehiclepitch which occurs when a heavy load is located rearwardly of axlehousing 14. When this condition occurs, the signal bellows 100 sensesthe fact that the front portion of the frame 12 is raised even furtherabove a desired relationship with the unsprung portions of the frontsuspension.

A pressure unbalance is created by the further extension of the frontsignal bellows and the rear signal bellows will be compressed more toproduce an opposed pressure differential in the control bellows 84, 86which acts on the control member 108 to compensate for the out of pitchcondition even though the rear height of the vehicle is at a desiredheight relationship. The correction for a high front end will maintainthe atmospheric valve 110 open and the vacuum valve 112 closed so thatthe pressure will increase in the bellows 62 to compensate for the extraload rearwardly of the axle housing by raising the frame a slight amountwhile lowering the front end of the frame. When the pitch of the frame12 is compensated, the pressure in the front and rear signal bellows 94,100 will be balanced and the pressure within the control bellows 84, 86will likewise be balanced so that the member 108 will assume a null orlevel position as illustrated in FIG. 1 at which point both of thevalves 110, 112 are closed.

When the load is removed, the reverse action occurs and the vacuum portis opened to pull the rear down to its level position and the frontsignal bellows 100 continues to operate to assure that the frame 12 willhave the desired pitch attitude.

In addition to the combined pitch and leveling control, the system ofFIG. 1 enables the operator of the vehicle to continually observe thepitch of the car by means of the indicator 82 moving with respect to theindicia 80 on the window 78 which is preferably located on the dashboardor instrument panel of the car.

Another aspect of the present invention is that the front and rearsignal bellows are located on the same side of the car so that roadmotions of the car do not cause any leveling action to take place. Theonly action will be changes in pitch on one side of the car which aregenerally representative of a like change of pitch on the other side ofthe car.

Another functional advantage of the system is the control of car diveduring braking and squat during acceleration, which is beneficial inmaintaining proper bumper heights at all time. The term pitch attitudeincludes attitude changes due to car dive or squat.

This basic control concept is independent of atmospheric pressure ofvariations thereof, and it is noncritical with respect to adjustment ofsystem if the final assembly is made with the car at an approximate curblevel position. Also, since the average operating pressure within thecontrol system is always at or near the ambient atmospheric pressure,the pressure differential stresses are minimized which enableslow-strength materials to be employed, such as plastics.

Although the leveling system described derives its energy from vacuum,other types of leveling system energy sources could be controlled by thebasic con ceptual technique represented by this invention.

The system can be used to alleviate diving of the car during brakestopping, so that bumper heights are maintained at all times. Thiscontrolled anti-dive is a further advantage of this invention.

Another embodiment of the invention is illustrated in FIGS. 2 and 6. 1nthe system of HO. 6, the vehicle has a rear suspension 114 likesuspension 16 in the first em- 7 bodiment. Other components of the rearaxle assembly 114 which correspond to like components illustrated in thefirst embodiment function in the same manner and have the same referencenumerals primed.

Likewise, the vehicle includes a front suspension 116 like the frontsuspension 34 of the first embodiment. The component parts of the frontsuspension 116 are identical'to those in the first embodiment and carrythe same reference numerals primed. However, in this embodiment of theinvention additional means are provided to give an active leveling ofthe front suspension by the provision of at least one operative activebellows 118 which is connected between the sprung and unsprung masscomponents of the front suspension 116 to vary the load carryingcapacity of the primary spring of the front suspension 116 to giveadditional pitch control in the vehicle.

More particularly, in this embodiment the active bellows 118 isconnected to one end of a pressure conduit 120 which has the oppositeend thereof connected to a port 122 leading to a sealed control chamber138 which communicates through a multiple component valve assembly 125with atmosphere or vacuum pipes 121, 123 depending upon the heightrelationship between the sprung and unsprung mass of the front of thecar.

As was the case in the previous embodiment, the active bellows 32' inthe rear assembly 114 is communicated with one end of a pressure conduit126 which has the opposite end thereof in communication with a controlport 127 which leads to a valve assembly 125 which communicates thepressure conduit 126 selectively to either an atmosphere pipe 128 or avacuum pipe 129.

The valve assembly 125 is coupled by linkage 130 to a pair of opposedcontrol bellows 132, 134 like the bellows 84, 86 in the firstembodiment. They are connected to sensing bellows 94, 100' like those inthe first embodiment through like components. The bellows 132, 134thereby produce a differential force on linkage 130 which positions thevalve assembly 125 to produce opposite leveling effects at the leveler118 and the leveler 32' to compensate vehicle pitch.

The diagrammatically illustrated valve assembly 125 and linkage 130 arepart of a controller and indicator assembly 136 shown in F168. 2 5,which more particularly includes a base portion 137 with a sealedchamber 138 therein closed by a cover 140 that engages an annular gasket142 formed around and supported on the top edge of the base 137. Thecover 140 is secured in place by screws 144.

On the other side of the base 137 is formed a second sealed chamber 147which is closed by a bottom cover 148.

In the illustrated arrangement, the linkage 130 includes an operatingshaft 150 which has a small diameter extension 152 thereon pivotallysupported within the lower cover 148. Shaft 150 also includes an upperbearing surface 154 that extends through a bore 155 in the base 137. Thebearing surface 154 is sealed by an annular O-ring 156 in the base bore155.

The shaft 150 is connected at a squared, upper end portion 158 thereofto the base 160 of a yoke member 162.

The yoke 162 has an upper slotted arm 164 and a lower slotted arm 166 inwhich are located pins 170, 172 located on either side of a movablepartition 176 formed between each of the bellows 132, 134.

An indicator stem 178 extends from the lower arm of the yoke and isconnected to an upstanding arm 180 movable with respect to a window 184on which is formed indicia 186 which indicates the pitch condition ofthe vehicle system in H0. 6.

The yoke has a cross-bar 188 formed thereon with ends 190, 192 connectedrespectively to stems 194, 196 of Schrader type tire valves 198, 200which control vacuum and atmospheric flow of air into the sealed chamber138 from whence the modulated air flows through the conduit 126 to therear leveler unit 32 for changing the height relationship between thesprung and unsprung mass portions of the rear suspension 1 14.

A lower cross-bar 202 like the upper cross bar has ends thereon that fitover stems 204, 206 of lower valves 208, 210 in the system which connectrespectively to vacuum and atmosphere.

The modulated pressure in the chamber 146 will be directed through thecontrol port 122 and conduit 120 to the front active bellows 118 so thatduring a pitch correction phase of operation when the pressure increasesin the bellows 32' it decreases in the bellows 118.

Thus, the valve assembly 125 operates to produce opposed pressures tothe chambers 138, 146. Hence, when leveler unit 32 acts in onedirection, leveler unit 118 acts in an opposite direction to give activefront and rear pitch compensation.

While the embodiments of the present invention, as herein disclosed,constitute a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. A front-to-rear vehicle pitch compensating system comprising: a rearsuspension assembly including a sprung and unsprung mass, a first loadleveling device between said masses for maintaining a predeterminedheight at the rear of the vehicle, a first signal bellows having apressurizable chamber therein responsive to the height relationshipbetween the sprung and unsprung mass portions of a vehicle at the rearthereof, a front suspension having a sprung and unsprung mass, a secondsignal bellows connected between the sprung and unsprung masses of saidfront suspension, said bellows including a pressurizable chamber forsensing the height relationship between the front sprung and unsprungmass portions, a controller including valve means, fluid supply meanscommunicating said controller and said load leveling device, meansresponsive to a differential pressure in said first and second signalbellows including means for operating said valve means to selectivelycommunicate first and second pressure sources with said fluid supplymeans, said first valve communicating said fluid supply means with thefirst pressure source to cause said leveling device to produce a firstsupplemental load carrying force when the rear of the vehicle is low toreturn it to the desired predetermined height, said controller beingoperative to condition said valve means to communicate said fluid supplymeans with the second pressure source when the front of the vehicle islow to cause said leveling device to produce a second supplemental loadcarrying force at the rear suspension which lowers the rear to maintaina predetermined desired pitch relationship between the front and rear ofthe vehicle.

2. A vehicle pitch control system comprising: a rear suspension havingleveler means with a pressurizable control chamber therein for producingchanges in the resultant load carrying capacity thereof to maintain adesired height between the sprung and unsprung mass of the rearsuspension, first signal means responsive to changes in the heightrelationship between the sprung and unsprung mass of the vehicle at therear thereof to produce a first signal, second signal means responsiveto changes in the height relationship between the sprung and unsprungmass of the vehicle at the'front thereof for producing a second signal,valve means for selectively connecting said leveler means to first andsecond pressure sources, valve actuator means for controlling said valvemeans in accordance with signals from said first and second signalmeans, said valve actuator means operating said valve means todisconnect said leveler means and said first and second pressure sourceswhen the car pitch is level, said valve actuator means responding to adifferential signal between said first and second signal meanscorresponding to a low front end pitch conuition to communicate one ofsaid pressure sources with said leveler means to reduce the heightrelationship between the sprung and unsprung mass of the vehicle at therear thereof to return the vehicle to a desired pitch attitude, saidvalve actuator means being responsive to a differential signal betweensaid first and second signal means reflecting a rear low vehicleattitude to connect said leveler means with the other pressure source toincrease the height relationship between the sprung and unsprung mass atthe rear of the vehicle thereby to return it to a desired pitchattitude.

3. A vehicle leveler control system and pitch attitude indicator for anautomobile leveling system comprising: a housing having a sealedpressure chamber, a supply conduit port to said chamber adapted to beconnected to a pressurizable leveler unit of a vehicle leveling system,first and second pressure supply ports on said housing adapted to beconnected to first and second pressure supplies, valve means forcontrolling flow from said pressure supply ports closed to said sealedchamber, valve actuator means including a level position wherein saidvalve means closes both of said ports, a front low operative positionand a rear low operative position, said valve actuator means beingoperative to close one of said valve and open the other of said valveswhen in one low position and to open said one of said valves and toclose the other of said valves when in its other operative low positionto selectively connect the supply port to the load leveler unit witheither said first or said second pressure supplies to change thepressure condition within the vehicle leveler unit to maintain acontrolled pitch attitude between the front. and rear of the vehicle,said control unit including an indicator panel thereon, indicator meansconnected to said valve actuator means and responsive to movementthereof into either its level or first and second low operative positionto indicate the pitch relationship between the front and rear of thevehicle during operation of the control device.

4. A vehicle pitch attitude controller and indicator comprising: a firstsignal producing means for producing a first signal responsive tochanges in the height relationship between the sprung and unsprungmasses of a vehicle at the front suspension thereof, a second signalproducing means for producing a second signal responsive to the-changesin the height relationship between the sprung and unsprung masses of thevehicle at the rear suspension thereof, pressurizable load leveler meansadapted to be connected between sprung and unsprung masses at the rearsuspension and sprung and unsprung masses at the front suspension, valvemeans for selectively applying first and second pressure sources to thepressurizable load leveler means for maintaining a predetermined pitchrelationship between the front and rear of the vehicle, valve actuatormeans for controlling said valve means including an operator responsiveto the signals produced by said signal producing means and operative toconnect said front leveler means to one of said pressure sources whileconnecting the rear leveler means to the other of said pressure sourcesto cause one of said leveler means to have an increased resultantlifting force on the sprung mass associated therewith while concurrentlycausing the other of said leveler means to have a reduced upliftingforce on the sprung mass associated therewith thereby to produce a frontto rear pitch attitude control.

5. A vehicle pitch attitude controller and indicator comprising: a firstsignal producing means for producing a first signal responsive tochanges in the height relationship between the sprung and unsprungmasses of a vehicle at the front suspension thereof, a second signalproducing means for producing a second signal responsive to the changesin the height relationship between the sprung and unsprung masses of thevehicle at the rear suspension thereof, pressurizable load leveler meansadapted to be connected between sprung and unsprung masses at the rearsuspension and sprung and unsprung masses at the front suspension, valvemeans for selectively applying first and second pressure sources to thepressurizable load leveler means for maintaining a predetermined pitchrelationship between the front and rear of the vehicle, valve actuatormeans for controlling said valve means including an operator responsiveto the signals produced by said signal producing means and operative toconnect said front leveler means to one of said pressure sources whileconnecting the rear leveler means to the other of said pressure sourcesto cause one of said leveler means to have an increased resultantlifting force on the sprung mass associated therewith while concurrentlycausing the other of said leveler means to have a reduced upliftingforce on the sprung mass associated therewith thereby to produce a frontto rear pitch attitude control, an indicator arm on said valve operator,said actuator means including opposed bellows for maintaining saidindicator in a null position when said first and said second signals arebalanced, said bellows responding to differences in said first andsecond signals to position said indicator arm to indicate the pitchattitude of the front and rear of the car.

6. A car pitch attitude indicator and controller device comprising: ahousing having a sealed compartment therein adapted to be communicatedwith the pressurizable control chamber of a vehicle leveler unit, a pairof opposed bellows supported in said housing each having an inletthereto, each of said bellows inlets adapted to be connectedrespectively to signal control bellows at the front and rear of the carfor producing bellows operation in accordance with the heightrelationship between the sprung and unsprung masses of the vehicle atthe front and rear thereof, a pair of pins on said bellows, a yokehaving spaced arms engaging said pins and a pivoted base, a pivot shaftthrough said base supported by said housing, first and second inletports in said housing, first and second valves adapted to connect saidinlet ports with a first and second source of pressure, said yoke havingmeans thereon to operate said valves to modulate the pressure withinsaid chamber upon bellows operation of said yoke, an indicator windowwith indicia thereon, and an indicator bar moved by operation of saidbellows with respect to said indicia to indicate car pitch.

1. A front-to-rear vehicle pitch compensating system comprising: a rearsuspension assembly including a sprung and unsprung mass, a first loadleveling device between said masses for maintaining a predeterminedheight at the rEar of the vehicle, a first signal bellows having apressurizable chamber therein responsive to the height relationshipbetween the sprung and unsprung mass portions of a vehicle at the rearthereof, a front suspension having a sprung and unsprung mass, a secondsignal bellows connected between the sprung and unsprung masses of saidfront suspension, said bellows including a pressurizable chamber forsensing the height relationship between the front sprung and unsprungmass portions, a controller including valve means, fluid supply meanscommunicating said controller and said load leveling device, meansresponsive to a differential pressure in said first and second signalbellows including means for operating said valve means to selectivelycommunicate first and second pressure sources with said fluid supplymeans, said first valve communicating said fluid supply means with thefirst pressure source to cause said leveling device to produce a firstsupplemental load carrying force when the rear of the vehicle is low toreturn it to the desired predetermined height, said controller beingoperative to condition said valve means to communicate said fluid supplymeans with the second pressure source when the front of the vehicle islow to cause said leveling device to produce a second supplemental loadcarrying force at the rear suspension which lowers the rear to maintaina predetermined desired pitch relationship between the front and rear ofthe vehicle.
 1. A front-to-rear vehicle pitch compensating systemcomprising: a rear suspension assembly including a sprung and unsprungmass, a first load leveling device between said masses for maintaining apredetermined height at the rEar of the vehicle, a first signal bellowshaving a pressurizable chamber therein responsive to the heightrelationship between the sprung and unsprung mass portions of a vehicleat the rear thereof, a front suspension having a sprung and unsprungmass, a second signal bellows connected between the sprung and unsprungmasses of said front suspension, said bellows including a pressurizablechamber for sensing the height relationship between the front sprung andunsprung mass portions, a controller including valve means, fluid supplymeans communicating said controller and said load leveling device, meansresponsive to a differential pressure in said first and second signalbellows including means for operating said valve means to selectivelycommunicate first and second pressure sources with said fluid supplymeans, said first valve communicating said fluid supply means with thefirst pressure source to cause said leveling device to produce a firstsupplemental load carrying force when the rear of the vehicle is low toreturn it to the desired predetermined height, said controller beingoperative to condition said valve means to communicate said fluid supplymeans with the second pressure source when the front of the vehicle islow to cause said leveling device to produce a second supplemental loadcarrying force at the rear suspension which lowers the rear to maintaina predetermined desired pitch relationship between the front and rear ofthe vehicle.
 2. A vehicle pitch control system comprising: a rearsuspension having leveler means with a pressurizable control chambertherein for producing changes in the resultant load carrying capacitythereof to maintain a desired height between the sprung and unsprungmass of the rear suspension, first signal means responsive to changes inthe height relationship between the sprung and unsprung mass of thevehicle at the rear thereof to produce a first signal, second signalmeans responsive to changes in the height relationship between thesprung and unsprung mass of the vehicle at the front thereof forproducing a second signal, valve means for selectively connecting saidleveler means to first and second pressure sources, valve actuator meansfor controlling said valve means in accordance with signals from saidfirst and second signal means, said valve actuator means operating saidvalve means to disconnect said leveler means and said first and secondpressure sources when the car pitch is level, said valve actuator meansresponding to a differential signal between said first and second signalmeans corresponding to a low front end pitch condition to communicateone of said pressure sources with said leveler means to reduce theheight relationship between the sprung and unsprung mass of the vehicleat the rear thereof to return the vehicle to a desired pitch attitude,said valve actuator means being responsive to a differential signalbetween said first and second signal means reflecting a rear low vehicleattitude to connect said leveler means with the other pressure source toincrease the height relationship between the sprung and unsprung mass atthe rear of the vehicle thereby to return it to a desired pitchattitude.
 3. A vehicle leveler control system and pitch attitudeindicator for an automobile leveling system comprising: a housing havinga sealed pressure chamber, a supply conduit port to said chamber adaptedto be connected to a pressurizable leveler unit of a vehicle levelingsystem, first and second pressure supply ports on said housing adaptedto be connected to first and second pressure supplies, valve means forcontrolling flow from said pressure supply ports closed to said sealedchamber, valve actuator means including a level position wherein saidvalve means closes both of said ports, a front low operative positionand a rear low operative position, said valve actuator means beingoperative to close one of said valve and open the other of said valveswhen in one low position and to open said one of said valves and Toclose the other of said valves when in its other operative low positionto selectively connect the supply port to the load leveler unit witheither said first or said second pressure supplies to change thepressure condition within the vehicle leveler unit to maintain acontrolled pitch attitude between the front and rear of the vehicle,said control unit including an indicator panel thereon, indicator meansconnected to said valve actuator means and responsive to movementthereof into either its level or first and second low operative positionto indicate the pitch relationship between the front and rear of thevehicle during operation of the control device.
 4. A vehicle pitchattitude controller and indicator comprising: a first signal producingmeans for producing a first signal responsive to changes in the heightrelationship between the sprung and unsprung masses of a vehicle at thefront suspension thereof, a second signal producing means for producinga second signal responsive to the changes in the height relationshipbetween the sprung and unsprung masses of the vehicle at the rearsuspension thereof, pressurizable load leveler means adapted to beconnected between sprung and unsprung masses at the rear suspension andsprung and unsprung masses at the front suspension, valve means forselectively applying first and second pressure sources to thepressurizable load leveler means for maintaining a predetermined pitchrelationship between the front and rear of the vehicle, valve actuatormeans for controlling said valve means including an operator responsiveto the signals produced by said signal producing means and operative toconnect said front leveler means to one of said pressure sources whileconnecting the rear leveler means to the other of said pressure sourcesto cause one of said leveler means to have an increased resultantlifting force on the sprung mass associated therewith while concurrentlycausing the other of said leveler means to have a reduced upliftingforce on the sprung mass associated therewith thereby to produce a frontto rear pitch attitude control.
 5. A vehicle pitch attitude controllerand indicator comprising: a first signal producing means for producing afirst signal responsive to changes in the height relationship betweenthe sprung and unsprung masses of a vehicle at the front suspensionthereof, a second signal producing means for producing a second signalresponsive to the changes in the height relationship between the sprungand unsprung masses of the vehicle at the rear suspension thereof,pressurizable load leveler means adapted to be connected between sprungand unsprung masses at the rear suspension and sprung and unsprungmasses at the front suspension, valve means for selectively applyingfirst and second pressure sources to the pressurizable load levelermeans for maintaining a predetermined pitch relationship between thefront and rear of the vehicle, valve actuator means for controlling saidvalve means including an operator responsive to the signals produced bysaid signal producing means and operative to connect said front levelermeans to one of said pressure sources while connecting the rear levelermeans to the other of said pressure sources to cause one of said levelermeans to have an increased resultant lifting force on the sprung massassociated therewith while concurrently causing the other of saidleveler means to have a reduced uplifting force on the sprung massassociated therewith thereby to produce a front to rear pitch attitudecontrol, an indicator arm on said valve operator, said actuator meansincluding opposed bellows for maintaining said indicator in a nullposition when said first and said second signals are balanced, saidbellows responding to differences in said first and second signals toposition said indicator arm to indicate the pitch attitude of the frontand rear of the car.